Cardiac amyloidosis
Specific changes in cardiac amyloidosis are caused by transthyretin amyloidosis (ATTR) or light-chain amyloidosis (AL).
T1-weighted axial slices demonstrate heterogeneous signal intensity, marked myocardial thickening of both ventricles, and a small amount of pericardial effusion. A key role is played by late gadolinium enhancement (Late gadolinium enhancement, LGE) in the short axis. Due to interstitial amyloid deposition and expansion of the extracellular space, characteristic absence of myocardial signal suppression (myocardial suppression) occurs.
Enhancement patterns:
- AL amyloidosis: more commonly characterized by a global subendocardial contrast distribution pattern.
- ATTR amyloidosis: typically characterized by a failure in myocardial nulling (failure in myocardial nulling) at any selected inversion time.
T1 mapping and extracellular volume fraction (ECV): These techniques outperform LGE in prognostic value because they allow for the quantitative assessment of diffuse interstitial expansion. Abnormal proteins in the intercellular space alter the aggregate relaxation time of the tissue, leading to an increase in native T1 (particularly significant in AL amyloidosis). Meanwhile, ATTR amyloidosis is associated with higher ECV values. Elevation of these markers can occur even before changes appear on standard clinical tests and LGE, making them ideal for early diagnosis.
Fabry disease (AFD)
Fabry disease is an intracellular (lysosomal) storage disorder. Consequently, the extracellular volume fraction (ECV) usually remains within normal limits, which helps differentiate it from interstitial pathologies.
Early markers and complications:
- Early biomarker: a low native T1 value of adipose tissue indicates the accumulation of glycosphingolipids in the myocardium. This sign appears even before left ventricular hypertrophy develops.
- Inferolateral wall involvement: late gadolinium enhancement (LGE) is typically detected in this area. Due to extensive fibrous replacement, the effect of scar tissue on the relaxation time overrides the effect of fatty inclusions. As a result, such patients exhibit pseudonormalization or even elevated T1 values.
Fibroelastosis and cardiac sarcoidosis
Magnetic resonance characteristics depend on the underlying disease substrate.
Fibroelastosis:
- T1-weighted images (spin-echo) reveal apparent myocardial thickening.
- Short tau inversion recovery (Short tau inversion recovery, STIR) clearly visualizes a thickened, hyperintense endocardium contrasting with the unaffected myocardium.
Cardiac sarcoidosis: The pathology presents as non-caseating granulomatous infiltration. Unlike diffuse amyloidosis, sarcoidosis causes focal (patchy) involvement of the heart muscle. Because the process frequently involves only small volumes of myocardial tissue, in the early stages the disease may not lead to left ventricular changes.
Briefly: answers to topical questions
What MRI signs and late gadolinium enhancement patterns are characteristic of cardiac sarcoidosis?
- Cardiac sarcoidosis (Cardiac sarcoidosis) is characterized by non-caseating granulomatous infiltration causing focal myocardial injury involving small volumes of tissue. T2-weighted images reveal intramural hyperintense foci and strands caused by edema. Late gadolinium enhancement (LGE) images show contrast uptake in these same areas. In the early stages, the disease may not cause left ventricular changes and may not be detected on LGE images.
Class and exam questions
Why does the ECV remain within normal limits in Fabry disease?
Because it is an intracellular (lysosomal) storage disorder. The pathological substrate accumulates inside the cells rather than in the interstitium, meaning the extracellular space does not expand.
How to differentiate AL and ATTR amyloidosis using late gadolinium enhancement data?
AL amyloidosis typically presents with a global subendocardial contrast distribution, whereas ATTR amyloidosis is characterized by a failure of myocardial signal nulling at any given inversion time.
Which MRI markers of amyloidosis appear earliest?
Native T1 mapping and ECV calculation. These parameters can increase at the earliest stages, even before signs of cardiac involvement appear on standard tests and LGE.
What explains the pseudonormalization of T1 in the inferolateral wall in Fabry disease?
Extensive fibrous replacement occurs in this area. Fibrosis increases T1, which compensates for and overrides the initial T1 reduction caused by glycosphingolipid accumulation.
What else to study on this topic
- Pathogenesis of transthyretin and AL amyloidosis
- Principles of native T1 mapping
- Methodology for calculating extracellular volume (ECV)
- Physical principles of the STIR sequence
- Histological appearance of non-caseating granulomas in sarcoidosis
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